This crossover trial is performed in advanced and metastatic pancreatic cancer not previously exposed to chemotherapy. The study compares a standard arm with gemcitabine plus erlotinib to an experimental arm with capecitabine plus erlotinib. It is the first trial of its kind to incorporate second-line treatment into the study design. Patient who fail on first-line therapy are switched to the comparator chemotherapy without erlotinib. The trial therefore not only compares two different regimens of first-line treatment, it also compares two sequential treatment strategies.